The use of standardized modular shipping containers has revolutionized the shipping industry. Modular shipping containers, often referred to as intermodal containers, freight containers, or simply containers, are reusable containers that can be used to ship products or raw materials from one location to another. Containers may be referred to as intermodal because the container may travel using many different modes of transit. For example, containers may travel by ship, rail, road, or any combination thereof.
The containers are made of a durable material, such as metal, in order to provide a reusable container that can withstand the harsh conditions associated with shipping. Containers are typically available in several standardized sizes. Several popular sizes of containers include 20, 40, and 53 foot versions. Typically, the exact size and form factors of a container are defined by a standards setting organization, such as International Organization for Standardization (ISO), Transit International Routier (TIR), Association of American Railroads (AAR) Standards, etc. Because the containers come in standard sizes, the complexity in handling the containers is greatly reduced. For example, a crane or forklift used to maneuver a container no longer needs to be adjusted to engage different size containers. The handling apparatus can be optimized to operate on a limited number of standardized sizes of containers.
Because the sizes of containers may be standardized across multiple modes of transport, there is no longer a need to unload and reload cargo from a container when the mode of transport changes. A standardized container may arrive via ship, be loaded onto a train, and then be delivered to a final destination via a truck. Throughout this process, the cargo within the container need never be removed from the container. Because the containers come in standard sizes, each of the modes of transport can be designed to operate with standard sized containers.
Specialized modular shipping containers exist for many different types of cargo. For example, tank containers exist for transporting liquids. Although the container may be specialized to hold a specific type of cargo, it should be understood that the overall size and form factor of the specialized container remains the same as a non-specialized container. The container handling equipment therefore need not be adjusted when dealing with specialized containers. From the perspective of the container handling equipment, all containers are handled exactly the same way, regardless of the type of cargo within the container.
Another example of a specialized container is a refrigerated shipping container, often times referred to as a reefer container, or simply a reefer. Reefers, as implied by the name, are used in situations where the cargo must be maintained at a specific temperature and/or humidity, the temperature usually being colder than the ambient temperature. In some cases, the required temperature may be higher than the ambient temperature. In either case, the term reefer, as used in the disclosure, will refer to a temperature and/or humidity controlled container, regardless of the container being heated or cooled.
Reefers, just as with all modularized containers, are designed to fit the size and form factors as defined by the standards organizations. Thus, reefers can be manipulated with the same handling equipment used to move normal containers. However, reefers present additional challenges that are not present with standard containers. For example, cargo being shipped in a reefer generally needs to be maintained within a specific range of temperature and/or humidity. If the temperature and/or humidity is out of range, even for a short period of time, the cargo may become unusable. For example, food products that are being shipped within a reefer may spoil if the temperature exceeds a defined threshold.
Therefore, there is a need to ensure that a reefer container maintains a temperature and/or humidity within a specified range for the duration of the reefer container's journey. Any anomalous variations in the temperature and/or humidity range within a container should be addressed as quickly as possible to prevent damage to the reefer container's cargo. Embodiments of the invention address these and other problems, individually and collectively.